This vehicle is equipped with one of the following antilock braking systems.
The vehicle is equipped with the following braking enhancement systems.
The following components are involved in the operation of the above systems.
The EBCM performs one initialization test each ignition cycle. The initialization of the EBCM occurs when the following conditions are met:
The initialization sequence briefly cycles each solenoid and the pump motor to verify proper operation of the components. In very cold ambient temperatures, vehicles equipped with JL4 may exhibit noticeable pump noise, and more than one cycle may be performed. The EBCM sets one or more DTCs in accordance with any malfunction that is detected.
The EBCM defines a drive cycle as the completion of the initialization sequence.
When wheel slip is detected during a brake application, the ABS enters antilock mode. During antilock braking, hydraulic pressure in the individual wheel circuits is controlled to prevent any wheel from slipping. A separate hydraulic line and specific solenoid valves are provided for each wheel. The ABS can decrease, hold, or increase hydraulic pressure to each wheel brake. The ABS cannot, however, increase hydraulic pressure above the amount which is transmitted by the master cylinder during braking.
During antilock braking, a series of rapid pulsations is felt in the brake pedal. These pulsations are caused by the rapid changes in position of the individual solenoid valves as the EBCM responds to wheel speed sensor inputs and attempts to prevent wheel slip. These pedal pulsations are present only during antilock braking and stop when normal braking is resumed or when the vehicle comes to a stop. A ticking or popping noise may also be heard as the solenoid valves cycle rapidly. During antilock braking on dry pavement, intermittent chirping noises may be heard as the tires approach slipping. These noises and pedal pulsations are considered normal during antilock operation.
Vehicles equipped with ABS may be stopped by applying normal force to the brake pedal. Brake pedal operation during normal braking is no different than that of previous non-ABS systems. Maintaining a constant force on the brake pedal provides the shortest stopping distance while maintaining vehicle stability.
The EBCM closes the isolation valve and keeps the dump valve closed in order to isolate the slipping wheel when wheel slip occurs. This holds the pressure steady on the brake so that the hydraulic pressure does not increase or decrease.
If a pressure hold does not correct the wheel slip condition, a pressure decrease occurs. The EBCM decreases the pressure to individual wheels during deceleration when wheel slip occurs. The isolation valve is closed and the dump valve is opened. The excess fluid is stored in the accumulator until the pump can return the fluid to the master cylinder or fluid reservoir.
After the wheel slip is corrected, a pressure increase occurs. The EBCM increases the pressure to individual wheels during deceleration in order to reduce the speed of the wheel. The isolation valve is opened and the dump valve is closed. The increased pressure is delivered from the master cylinder.
The dynamic rear proportioning (DRP) is a control system that replaces the hydraulic proportioning function of the mechanical proportioning valve in the base brake system. The DRP control system is part of the operation software in the EBCM. The DRP uses active control with existing ABS in order to regulate the vehicle's rear brake pressure.
The red brake warning indicator is illuminated when the dynamic rear proportioning function is disabled.
When drive wheel slip is noted while the brake is not applied, the EBCM will enter traction control mode.
The EBCM uses a 5-volt pulse-width modulated (PWM) signal to request the PCM to reduce the amount of torque to the drive wheels. The PCM reduces torque to the drive wheels by retarding spark timing and by commanding the throttle actuator control. The PCM uses a 5-volt PWM signal in order to report to the EBCM the amount of torque delivered to the drive wheels.
The vehicle stability enhancement system (VSES) adds an additional level of vehicle control to the EBCM. Yaw rate is the rate of rotation about the vehicle's vertical axis. The VSES is activated when the EBCM determines that the desired yaw rate does not match the actual yaw rate as measured by the yaw rate sensor.
The desired yaw rate is calculated from the following parameters:
The difference between the desired yaw rate and the actual yaw rate is the yaw rate error, which is a measurement of oversteer or understeer. If the yaw rate error becomes too large, the EBCM attempts to correct the vehicle's yaw motion by applying differential braking to the left or right front wheel. The amount of differential braking applied to the left or right front wheel is based on both the yaw rate error and side slip rate error.
The VSES activations generally occur during aggressive driving, in turns or on bumpy roads without much use of the accelerator pedal. When braking during VSES activation, the pedal pulsations feel different than the ABS pedal pulsations. The brake pedal pulsates at a higher frequency during VSES activation.
The instrument panel cluster (IPC) illuminates the brake warning indicator when the following occurs:
The IPC illuminates the ABS indicator when the following occurs:
The low traction indicator is part of the traction control switch. The EBCM applies ground to the traction control active signal circuit in order to illuminate the low traction indicator during a traction control event.
The low traction indicator is located in the instrument panel cluster. The EBCM applies ground to the traction control active signal circuit in order to illuminate the low traction indicator during a traction control event.
The traction off indicator, which is part of the traction control switch, turns OFF when ground is applied to the service traction control signal circuit. The EBCM illuminates the traction off indicator if any of the following conditions are present.
The EBCM inhibits the traction control system when a TCS-disabling malfunction occurs, or when the automatic engagement feature is programmed to disable the TCS when the ignition is turned ON. Refer to Programming the Traction Control Automatic Engagement Feature.
The traction off indicator, which is located in the instrument panel cluster, turns OFF when ground is applied to the service traction control signal circuit. An inverting driver module is used in order to apply ground to the traction off indicator control circuit when indicator illumination is requested. The EBCM illuminates the traction off indicator if any of the following conditions are present.
STABILITY SYSTEM ACTIVE is displayed on the message center when a VSES or TCS event is taking place. The EBCM requests this display via a Class 2 message.
STABILITY SYSTEM LIMITED is displayed on the message center for one or more of the following conditions:
STABILITY SYSTEM DISABLED is displayed on the message center for one or more of the following conditions:
SERVICE STABILITY SYSTEM is displayed on the message center when any VSES DTC is set.
The indicator lamp on the stability system mode switch indicates the state of the system. The indicator lamp is ON when the VSES is in stability system full mode or limited mode and the system is initialized.
The indicator lamp is OFF under any of the following conditions:
The automatic engagement feature may be programmed so that the traction control system activates or does not activate automatically at the start of each ignition cycle. In order to change the status of the automatic engagement feature, perform the following procedure:
Important: Failure to follow the correct procedure may cause DTC C0283 to set in EBCM memory.
